Fatherland

Very similar to Prussia, except that this is not an outrageously stereotyped portrayal of Imperial Germany, but an Ersatz-Kaiserreich with any degree of accuracy and outrageousness. Tell-tale signs include:

Pickelhauben.
Arrogant aristocrats, duelling scars and monocles optional.
The military is all-pervasive.
Gratuitous German. Or something that sounds like it. Or something that some people think sounds like it.
Confusion as to whether this is the Kaiserreich or the Nazis.
Vaguely WWI-ish technology, especially ugly box-shaped tanks, U-Boats, and, of course, zeppelins.
Great big black eagles and Iron Crosses everywhere, or an obvious stand-in for them.

Of course, there might be an example which is a well-done historical allegory full of accurate representations of the Imperial period, but hey, why bother?

Compare Glorious Mother Russia for similar parent-country symbolism.

Examples of Fatherland include:

Anime and Manga

The Royal Empire in Pumpkin Scissors.
The nation of Amestris in Fullmetal Alchemist. With the added bonus that it was created as part of a plan by someone referred as "Father", making it a literal Fatherland
One of the sides in Legend of the Galactic Heroes is essentially Fatherland Recycled in Space.

Comic Books

Bretzelburg in Spirou and Fantasio is a Ruritanian country with conspicuous Fatherland trappings. The soldiers wear Picklehaube helmets and much of the rest is straight out of Nazi Germany.
Ancient Germania in Asterix and the Goths fits this trope, featuring elements of Imperial Germany (e.g. Pickelhauben), Nazi Germany (e.g. a red flag with a black eagle in a white circle), and even (at the time of the comic's creation) contemporary Germany (Visigoths and Ostrogoths as stand-ins for West Germany and East Germany respectively). Oh yeah, and to make the Anachronism Stew complete, the story of course takes place in 50 BC, like in all Asterix comics.

Video Games

The Badds in Bionic Commando.
The Rahmos Empire from Iron Grip, though it is a Fantasy Counterpart Culture and overlaps a bit with Tsarist Russia and Reds with Rockets in some of its esthetics. Ironically, their arch-enemies, the Fahrongi, have the occasional pickelhaube-wearing soldier, while Rahmosians have none.

Western Animation

Sombertown in Santa Claus is Comin' to Town, what with the Burgermeister and Grimsby in his pickelhauben.